Molecular Basis of Postischemic Maladaptation in the Insulin Resistant Heart

摘要 2型糖尿病已达到流行病的比例，是冠心病的主要原因， 美国的胰岛素抵抗是2型糖尿病的标志，与2 - 4倍的高风险相关。 急性心肌梗死（MI）后的心脏病发病率和死亡率。该项目的目标是 阐明心肌梗死后胰岛素抵抗与心脏恢复不良的分子机制， 这一知识，以制定治疗策略，改善糖尿病患者的心脏功能恢复 在再灌注时。解偶联蛋白3（Uncoupling protein 3，UCP 3）是一种线粒体阴离子载体蛋白，具有抗氧化作用 参与长链脂肪酸（LCFA）的代谢。肌肉UCP 3含量在2型中低50% 糖尿病患者与健康对照组比较。在小鼠的心脏中也观察到类似的减少 以及患有胰岛素抵抗和2型糖尿病的大鼠。在大鼠中使用CRISPR/Cas9靶向突变， 收集的初步数据显示，心脏UCP 3水平降低50%足以显著降低 缺血后收缩恢复受损。我们的研究结果进一步表明，功能恢复减少， 缺血后胰岛素抵抗和UCP 3缺乏的心脏是由有限的氧化LCFA的能力引起的， 再灌注，可以通过提供中链脂肪酸（MCFA）作为替代燃料来挽救的缺陷。 除了生物能缺陷之外，已知受损的LCFA氧化会导致长链脂肪酸的毒性积累。 神经酰胺和增加氧化应激。因此，我们假设UCP 3的减少损害了 限制心肌LCFA对胰岛素抵抗心肌梗死后收缩功能的恢复 氧化、增加线粒体功能障碍和增加再灌注时心肌细胞死亡。 三个目标将解决这一假设的小鼠和大鼠模型的饮食，饮食，或遗传 在多系统方法中诱导心肌胰岛素抵抗或UCP 3缺乏（降低40-50%） 将MI/再灌注的体内模型与分离的跳动心脏和分离的线粒体相结合。目标1将 检查UCP 3缺乏及其逆转对心脏结构和功能恢复的影响， MI/再灌注。目的2将研究UCP 3缺陷对线粒体的分子影响， 缺血/再灌注期间心脏功能和心脏氧化代谢的变化。目标3将测试代谢 基于增加MCFA对心脏的供应的干预可以逆转这些异常。我们预计这一 揭示2型糖尿病患者预后不良的新分子机制的项目 在MI/再灌注后，它将为测试基于MCFA的治疗的其他研究提供基础。 作为改善MI后再灌注的T2 DM患者心脏结局的代谢策略。

ABSTRACT Type 2 diabetes has reached epidemic proportions and is a leading cause of coronary heart disease in the United States. Insulin resistance, a hallmark of type 2 diabetes, is associated with a 2 to 4 times higher risk of cardiac morbidity and mortality following acute myocardial infarction (MI). The goals of this project are to elucidate the molecular mechanisms linking insulin resistance to poor cardiac recovery after MI and to apply this knowledge to develop therapeutic strategies for improving recovery of cardiac function in diabetic patients at reperfusion. Uncoupling protein 3 (UCP3) is a mitochondrial anion carrier protein with antioxidant properties involved in the metabolism of long-chain fatty acids (LCFA). Muscle UCP3 content is 50% lower in type 2 diabetic patients compared with healthy control subjects. A similar decrease is observed in the heart of mice and rats with insulin resistance and type 2 diabetes. Using CRISPR/Cas9-targeted mutation in rats, we have gathered preliminary data showing that a 50% decrease in cardiac UCP3 levels is sufficient to significantly impair contractile recovery following ischemia. Our results further suggest that decreased functional recovery of insulin resistant and UCP3 deficient hearts after ischemia is caused by a limited capacity to oxidize LCFA at reperfusion, a defect that can be rescued by supplying medium-chain fatty acids (MCFA) as an alternative fuel. Besides the bioenergetic deficit, impaired LCFA oxidation is known to cause a toxic accumulation of long-chain ceramides and to increase oxidative stress. Therefore, we hypothesize that decreased UCP3 impairs the recovery of systolic function in insulin resistant hearts following MI by limiting myocardial LCFA oxidation, increasing mitochondrial dysfunction, and increasing cardiac myocyte death at reperfusion. Three aims will address this hypothesis in mouse and rat models of dietary, pharmacologically, or genetically induced myocardial insulin resistance or UCP3 deficiency (40-50% decrease) in a multisystem approach combining in vivo models of MI/reperfusion to isolated beating hearts to isolated mitochondria. Aim 1 will examine the effect of UCP3 deficiency and of its reversal on cardiac structural and functional recovery post MI/reperfusion. Aim 2 will investigate the molecular consequences of UCP3 deficiency for mitochondrial function and cardiac oxidative metabolism during ischemia/reperfusion. Aim 3 will test whether a metabolic intervention based on increasing supply of MCFA to the heart can reverse these abnormalities. We expect this project to reveal a novel molecular mechanism responsible for the poor prognosis of type 2 diabetic patients following MI/reperfusion, and that it will provide the basis for additional studies to test MCFA-based treatments as a metabolic strategy to improve cardiac outcomes in T2DM patients undergoing reperfusion after MI.